1. Field of the Invention
This invention relates to a twin check valve water meter having a pair of check valves that are strategically positioned at both the inlet and outlet ends thereof. The twin check valve water meter is connected between a source of water (e.g. a fire hydrant) and a water receptacle (e.g. a tanker truck) and adapted to prevent back flow and the possibility of introducing non-potable water from the tanker truck to the water supply of a municipality via the fire hydrant.
2. Background Art
Water meters have long been employed to measure the volume of water that is taken from a source. For example, a tanker truck used by fire departments and construction companies must have an available supply of water to be transported from place-to-place and delivered on demand. Because of the large volume of water to be consumed, such tanker trucks are typically filled at a fire hydrant. A water meter is coupled to the fire hydrant so as to measure the volume of water that is withdrawn from the water supply of a local municipality. Once the truck is filled, an indication of water use is recorded so that the municipality can issue a charge to the user in order to be reimbursed for the water that has been consumed via the fire hydrant.
During the process of filling the tanker truck, a rupture in the water main of the municipality to which the fire hydrant is linked has been known to cause the water stored within the tanker truck to be suctioned therefrom and introduced back to the municipal water supply. Such back flow of water from the tanker truck is often characterized by potentially harmful bacteria. That is to say, by the time the water main has been repaired, the water supply of the municipality may be contaminated by the back flow of water from the tanker truck via the fire hydrant such that residents of the municipality could be subjected to potential illness.
To reduce the possibility of back flow of non-potable water from a tanker truck to a water supply at a fire hydrant, water meters have incorporated unidirectional flow control devices. So as not to effect the accuracy of the water register, conventional water meters that are coupled to a fire hydrant are known to include a pair of check valves located at the outlet end thereof and downstream from the register. Placing the pair of check valves at the outlet end results in conventional water meters being undesirably long, heavy and bulky. What is more, a sometimes turbulent, uneven flow of water is supplied to the water meter from the fire hydrant so as to adversely effect the accuracy of the water meter register such that the charges to the water user could be erroneous.
Therefore, what is needed is a water meter to be coupled to a fire hydrant and adapted to provide a smooth, linear flow of water from the fire hydrant to the water register and reliably prevent the back flow of non-potable water from a tanker truck to the fire hydrant while, at the same time, minimizing the size and weight of the water meter.
In general terms, a twin check valve water meter is disclosed having an inlet end to be coupled to a source of water (e.g. a fire hydrant) and an outlet end to be coupled to a water receptacle (e.g. a tanker truck) of the end user. The water meter includes a register by which to measure the volume of water flowing therepast so that the end user can be billed for its water consumption.
Water from the fire hydrant is received by the water meter at an inlet gate valve housing which encloses an inlet gate valve. From the inlet gate valve housing, the water flows into an inlet check valve housing containing a first check valve. The inlet check valve housing is located ahead of (i.e. upstream from) the water register. A flat perforated screen is located at the interface of the inlet check valve housing and a strainer housing. The strainer housing has a series of guide rails and blocks that cooperate to slidably receive and lock into place a perforated wave-shaped strainer. The strainer housing within which the strainer is disposed lies in fluid communication with a turbine housing of the twin check valve water meter. The water register sits atop the turbine housing and includes a turbine assembly to measure the volume of water flowing from the fire hydrant to the tanker truck. The twin check valve water meter also includes an outlet check valve housing containing a second check valve. The outlet check valve is located behind (i.e. downstream from) the water register. The outlet check communicates with an outlet gate valve housing which encloses an outlet gate valve.
Unlike conventional water meters, the twin check valve water meter of this invention has a check valve located at each of the inlet and outlet ends thereof (i.e. both upstream and downstream from the water register). Thus, not only will back flow from the tanker truck to the fire hydrant be reliably prevented, but the overall size and weight of the water meter may be advantageously reduced relative to such conventional water meters. Moreover, by locating the flat screen and wave-shape strainer in the flow path ahead of the water register, the sometimes turbulent water stream supplied from the fire hydrant will be slowed and smoothed to a linear flow, whereby to maximize the accuracy of the reading of the water register.